This Mentored Clinical Scientist Developmental Award application describes a program of career development and training for the applicant, who has completed a residency in pediatrics and a fellowship in pediatric cardiology. This program will be under the mentorship of Dr. Scott Rivkees, who has experience grooming young M.D. and Ph.D. trained scientists for independent research and who is a recognized leader in the field of receptor biology. The applicant intends to study the origins of abnormal heart development by using his expertise in muscle cell biology and in the physiology of congenital heart lesions and by continuing his training in developmental molecular biology. The research plan presented herein will focus on the role of intracellular calcium signals in controlling cardiac development. Calcium's role as an intracellular messenger is well-recognized. Preliminary data demonstrate that alterations in intracellular calcium levels and the signal cascades that lie downstream of calcium can dramatically alter cardiac development. In addition, previous studies have demonstrated the presence of calcium regulatory mechanisms in the early mammalian heart. To further understand these phenomena, following Specific Aims are proposed. (1) I will examine whether a reduction of intracellular calcium levels affect cardiac myocyte differentiation and cardiac morphogenesis. (2) I will examine the role of CaMK II in the regulation of cardiac morphogenesis and myocyte differentiation. Finally, (3) I will determine whether calcium signals modulate TAF expression and function in the developing heart. Yale University is a world leader in biomedical research, and the Department of Pediatrics has proven itself to be an ideal setting to train pediatric physician-scientists. A prestigious advisory committee drawn from the faculty at Yale will monitor the applicant's progress during this project. Combined with Dr. Rivkees mentorship, these resources should allow the applicant to develop into a successful independent investigator and make great contributions to the field of developmental cardiology.